Hard disk drives are conventionally known information storage devices that are to be incorporated into or connected to an electronic apparatus, such as a personal computer and a word processor. A typical hard disk drive comprises a disk serving as an information storage medium, a head for reading/writing recording bits from/to the disk, an arm for holding the head in the vicinity of the disk, and an electromagnetic actuator for driving the arm to move the head along the disk.
With the development of the personal computers and the like, the hard disk drives have become higher in recording density. In particular, the personal computers or the like have become increasingly required to process image data or music data in recent years, and accordingly, the recording density of the hard disk drives has been dramatically increased. With the increase in the recording density of the hard disk drives, recording bits on a disk have become finer and the rotational speed of the disk has become higher, and therefore, it has become required to position the head more precisely in a shorter time. In addition, miniaturization and power saving of the hard disk drives are being promoted.
There has been proposed a hard disk drive which has, in addition to the conventional electromagnetic actuator, a piezoelectric actuator provided in the middle of the arm to position the head more precisely in a shorter time.
However, the piezoelectric actuators and hard disk drives proposed in the past have disadvantages in that they can only provide an insufficient displacement of the head, need a high driving voltage, are bulky and heavy, have a large moment of inertia of the head when the head is driven and are produced at a high cost.
These disadvantages are not specific to the hard disk drives but are common to the types of information storage devices that have a head held and moved by an arm.